Flow-rate activated safety vacuum release system

ABSTRACT

A Safety Vacuum Release System (SVRS) which incorporates a water flow-rate sensor in electrical communication with the electric motor which powers a swimming pool pump at an aquatic facility. When the flow of water drops to a rate indicative of a flow blockage at a suction outlet fitting within the pool, the SVRS shuts down the electric pump motor to release a suction entrapped bather. In one embodiment, the flow-rate sensor can be a transit time or a Doppler unit which features a non-invasive, clamp-on installation onto the circulation pipe. The SVRS can display the real-time rate of flow of the circulation system, the real-time turnover rate of the swimming pool, and signal the operator when it is time to clean the pool filter. The SVRS can also maintain the optimum flow rate of the circulation system by adjusting the speed of a variable speed pump motor as hydraulic resistance changes.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional No.61/386,713 entitled “FLOW RATE ACTIVATED SAFETY VACUUM RELEASE SYSTEM”,naming Joseph D. Cohen as inventor and filed on Sep. 27, 2010, theentirety of which is hereby incorporated by reference and U.S.Provisional No. 61/525,339 entitled “FLOW RATE ACTIVATED SAFETY VACUUMRELEASE SYSTEM”, naming Joseph D. Cohen as inventor and filed on Aug.19, 2011, the entirety of which is hereby incorporated by reference

FIELD OF THE DISCLOSURE

The present disclosure relates to a safety vacuum release system(“SVRS”) for use with suction entrapment events in aquatic facilities.More specifically, the disclosure relates to the detection of anunderload condition in a swimming pool circulation pump motor and aresponsive shutdown of the pump motor. In addition, the presentdisclosure relates to suction entrapment safety vacuum release systemsfor use with aquatic facilities which monitors the actual flow-rate ofwater in the circulation system and responds to abnormally lowflow-rates indicative of a suction entrapment condition.

BACKGROUND

Swimming pools and other aquatic facilities typically require acirculation system to remove water, filter the water, optionally heatthe water, and return the processed water to the facility. A circulationpump draws water from the facility by generating a vacuum or a region ofnegative pressure and pumps the water back to the facility underpositive pressure. Typically, the circulation pump produces considerablenegative pressure through various intake pipes connected to suctionoutlet fittings within the pool.

Two types of prior art SVRS have been developed and commercialized. Onetype reacts to the increase in the vacuum pressure, which is apotentially lethal force capable of holding a bather against an intakeof the water circulation system, and then reduces the vacuum level byeither injecting fluid or gas (water or air) at atmosphere pressure intoportions of the circulation system piping, or shutting off thecirculation pump, or both. The normal operating vacuum pressure level ofswimming pool pumps varies from pool to pool and is affected by a numberof factors. These factors include the diametric size of the piping,length of the intake pipe run, the elevation of the pump in relation tothe pool water level, the overall hydraulic resistance of thecirculation system, the pool operation being performed, and thehorsepower of the pump. Therefore, the critical life-saving function ofthese SVRS is dependent upon the correct site specific calibration ofthe SVRS. Therefore prior art SVRS may be subject to fail, should it notbe properly calibrated.

Undesirably, normal operating conditions of a swimming pool, includingthose conditions found in the operation of manual and/or automaticvacuum systems, as well as impeded water circulation through debrisladen skimmers and drain grates, can cause an increase in vacuumpressure that will undesirably trigger some existing SVRS when thereactually is no flow stoppage or potential suction entrapment accident.

A second type of commercially available SVRS reacts to the load factorchange of the electric motor which powers the circulation pump. The loadfactor of the circulation pump motor is most commonly measured as thepower factor of the motor, which may be defined as the percentage ofpower being converted into energy divided by the amount of powerconsumed. Motor load can also be measured by motor voltage, amperage, orshaft speed measured as revolutions per minute (“RPM”). The load factorof a circulation pump motor is directly related to the rate of fluidflow through the pump. When the water flow is blocked within theswimming pool, the circulation pump motor may experience an underloadcondition, that is, the motor power factor decreases and the shaft RPMincreases. With this second type of SVRS, the underload conditiontriggers a shutdown of the circulation pump as a safety releasemechanism.

This second type of SVRS has three major drawbacks. First, this type ofSVRS has a narrow operating range of water flow-rate; second, the SVRShas an undesirable time delay for an underload condition to manifestafter a water flow blockage has occurred. Third, this type of SVRSgenerally does not operate well when the pump is installed below theswimming pool water level.

More specifically, the load on the circulation pump motor decreasesapproximately 13% when the water circulation system changes from normalwater flow conditions to a blocked intake flow condition. Setting theload-sensor to shut off the motor when the load drops by this smallamount only allows for a narrow operating range of water flow fromnormal water flow conditions to minus 30%. Typically, a 1 HP swimmingpool filter system operates at 65 GPM. With this type of SVRS, the pumpwill shut off when the flow drops below 45 GPM. Manual or automaticvacuums, in-floor cleaner systems, or operating with a dirty filter ordebris laden skimmer baskets and drain grates will impede the flow ofwater to less than 45 GPM and cause this type of SVRS to become anuisance and shut the pump off when no hazard exists. Both types of theaforementioned SVRS have inherent problems with flooded intakecirculation pumps, or pumps installed below the water level of theswimming pool which they are serving.

Therefore, it is desirable to employ load-sensing technology orflow-rate sensing technology as an accurate and responsive technique fordetermining occurrence of an aquatic suction entrapment event. Thereexists a need for an effective SVRS that requires substantially noadditions in order to retrofit an existing circulation system.

Therefore, it is desirable to employ load-sensing technology orflow-rate sensing technology as an accurate and responsive technique fordetermining occurrence of an aquatic suction entrapment event.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a safety vacuum releasesystem (“SVRS”) that can be used to retrofit substantially any swimmingpool circulation system by the direct substitution of the circulationpump motor or the inclusion of a flow-rate sensor, thereby requiringsubstantially no expansion of equipment space, housings, and the like.

In one embodiment, an aquatic facility with a safety vacuum releasesystem includes an aquatic vessel configured to contain a body of watersuitable for bathing. The aquatic facility also has a circulation systemfor circulating the body of water that includes at least one circulationintake, a circulation pump that includes a pump intake in fluidcommunication with the circulation intake and a pump output in fluidcommunication with a circulation output for directing the water backinto the aquatic vessel, and an electric motor for operating thecirculation pump. The aquatic facility also includes a flow-rate sensorin fluid communication with the circulation system to measure the rateof flow of the water circulated by the circulation system (gallons perminute). The safety vacuum release system is in communication with thecirculation system and the flow-rate sensor. The safety vacuum releasesystem interrupts the operation of the circulation pump in response to aparticular flow-rate measured by the flow-rate sensor, pre-determined tobe low enough to be caused by a blockage at a suction outlet fitting.

In another embodiment, a flow-rate activated safety vacuum releasesystem includes a circulation system for an aquatic vessel and aflow-rate sensor operably engaged to the circulation system. Theflow-rate sensor is configured to determine a rate of flow through thecirculation system. The flow-rate activated safety vacuum release systemalso includes a control system in communication with the flow-ratesensor configured to receive a signal related to the flow-rate throughthe circulation system. The control system also provides one or morecontrol signals to a pump of the circulation system.

A method for automatically releasing a bather suction entrapped in anaquatic vessel having a water circulation system is disclosed herein.The method may be used to free the trapped bather being held by suctionat a submerged suction outlet fitting of the water circulation system.The method includes circulating water in the water circulation systemwith a pump powered by a motor. The water circulation system has anormal operating range defined by a minimum allowable flow-rate and amaximum allowable flow-rate. The method also includes identifying anoccurrence of an excessive vacuum pressure within the submerged intakeof the water circulation system, decreasing the excessive vacuumpressure within the submerged suction outlet fitting by interrupting thepower applied to the pump, and releasing the trapped bather from thesubmerged intake.

In various other embodiments, the systems and methods disclosed hereinmay be encoded on computer-readable media that may be executed by aprocessor. An additional aspect of the present disclosure is to providean SVRS that protects the pump against damage that can result fromrunning dry. Correspondingly, this SVRS maintains the continuity of thewater content of the circulation system and does not introduce air intothe circulation system. Similarly, this SVRS does not cause the pump tolose prime, thereby enabling the circulation system to restart withminimum difficulty.

Another aspect is to provide an SVRS that requires no hydraulicconnections to the fluid circulation system of the swimming pool. Uniqueto this disclosure is that this SVRS is non-invasive because it is notin direct fluid communication with the circulation system and requiresno hydraulic connections. Connections like pressure sensor lines,reversing valves, and pressure relief valves are not needed with thisdisclosure.

A further aspect of the present disclosure to enable the efficient andeconomical design or upgrade of pool circulation systems by the suitableselection of a motor equipped with load-sensor. The relatively simpleselection or exchange of a motor is far more economical that installingsupplemental piping, valves, and like bulky equipment previouslyrequired.

Another aspect of the present disclosure is to provide an SVRS that canbe completely built into and incorporated within a swimming pool pumpmotor. A similar aspect is to provide an SVRS that can be retrofitted toa swimming pool simply by changing out a circulation pump motor, whichis a relatively standard maintenance procedure for any pool.

One aspect is to provide a readily available and easily implementedsolution to suction entrapment, which swimming pool pump manufacturerscan incorporate into their pumps with little burden on establishedpractices. An additional aspect is to provide an SVRS that is likely tobe of exceptionally low cost, thus enabling a greatly increased range ofpool owners to improve the safety of their pools by outfitting the poolswith an SVRS. Another aspect is to expand the scope of applications forwater flow-rate sensing technology to include this new application as alife saving device for swimming pools.

According to one aspect of the disclosure, an aquatic facility isequipped with a safety vacuum release system that detects underload ofthe motor powering the circulation pump. The facility provides anaquatic vessel that contains a body of water having at least onecirculation suction outlet fitting (drain) near a bottom of the aquaticvessel. A circulation pump has an intake side for drawing water out ofthe aquatic vessel and an output side for directing water back into theaquatic vessel. A suction line interconnects the suction outlet fittingand the intake side of said circulation pump, and a return lineinterconnects the vessel and the outlet side of the circulation pump. Anelectric motor operates the circulation pump when said motor operatesand shuts off the pump when the motor is shut off. A suitable flow-ratesensor device connected to the suction line may measure a flow-rateoutside of a predetermined operating range indicative of a blockage atthe suction line, and the safety vacuum release system controls a switchupon the detection of the undesired flow-rate to shut off the motor.

Another aspect of the disclosure provides a method of detecting asuction entrapped blockage at a suction outlet fitting supplying theintake side of a circulation pump with water flow of an aquatic facilityand releasing the blockage. The method steps include powering thecirculation pump by an electric motor; sensing a flow-rate changeindicative of a blockage held by vacuum at a suction outlet fitting;shutting off the electric motor in response to detection of theflow-rate change, and releasing the blockage at the suction outletfitting by retaining the motor in shut-off status for a time sufficientto allow the vacuum to neutralize.

In one aspect, the present disclosure provides an SVRS for an aquaticfacility which monitors and reacts directly to changes in the flow-rateof the water passing through the aquatic facility water circulationpump. In another aspect, the present disclosure provides an SVRS for anaquatic facility which will both reliably and quickly release suctionentrapped bathers by shutting off the water circulation pump motorwithout delay. Yet another aspect of the present disclosure is to shutdown the water circulation pump and provide release for a potentialsuction entrapment incident before a complete blockage occurs.

A further aspect of the present disclosure provides an aquatic facilityoperator with a real-time readout of the actual rate of flow of thewater through the water circulation pump system. Another aspect of thepresent disclosure provides an SVRS which will function reliably on allpool circulation pumps regardless of their elevation in relation to thepool water level.

Yet another aspect of the present disclosure provides an SVRS which willfunction reliably in all types of flooded suction pump installationsindependently of the pump's relationship to the aquatic facility waterlevel. A further aspect of the present disclosure provides an SVRS whichis operable over a wide range of water flow-rates for an aquaticfacility water circulation pump system to permit an aquatic facilityoperator to perform normal facility maintenance operations withoutproblematic pump shutdowns often caused by prior art SVRS.

These and other aspects, advantages and novel features of the presentdisclosure will become apparent from the following description of thedisclosure when considered in conjunction with the supplementalmaterials provided in support thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a swimming pool with SVRS built intothe water circulation system according to one embodiment.

FIG. 2 is a block diagram of a motor system including a load-sensoraccording to one embodiment.

FIG. 3 is a schematic diagram of a flow-rate activated SVRS according toone embodiment.

FIG. 4 is a block diagram of a computing device for operating the SVRSaccording to one embodiment.

DETAILED DESCRIPTION

The present disclosure relates to is a safety vacuum release system(“SVRS”). An SVRS is an automatic safety system in an aquatic facilitysuch as a swimming pool, spa, wading pool, or like aquatic vessel thatin use contains a body of water. Such a system automatically releases ablocking object that blocks a single-sourced circulation pump.Typically, the blockage is a bather who has become trapped onto asuction outlet fitting, which typically communicates through a suctionconduit with a circulation pump. Via the conduit, the circulation pumptypically found in an aquatic facility is capable of producing adangerously high vacuum level at a suction outlet fitting if intake flowto the pump is blocked. The level of suction can be high enough that abather cannot free himself from a suction outlet fitting unless releasedby a SVRS. Suction entrapment can drown or otherwise injure a trappedbather unless the victim is quickly released.

Circulation systems are present in substantially all aquatic facilities.Such systems are necessary for filtration, sanitization, heating,hydrotherapy, and the operation of water features such as decorativefountains. A circulation pump provides the water flow within thesecirculation systems. An electric motor is connected to the pump toprovide motive power.

The disclosure relates to systems and methods of sensing and respondingto blockage or bather entrapment at suction outlet fittings. Variousembodiments of the present disclosure relate to the systems and methodsdisclosed in co-owned U.S. patent application Ser. No. 11/163,860,entitled “Load Sensor Safety Vacuum Release System,” the contents ofwhich are incorporated herein by reference in its entirety.

In various embodiments, load-sensing systems monitor the operation of anelectric pump motor and determine the power level that the motor isproducing. These systems detect overload and underload conditions. Suchsystems can shut off the motor in response to sensing an undesirableoverload or underload condition. The intended purpose of these systemsis to protect against damage to the motor or to an associated, poweredmachine or the product being produced by the machine. Such systems alsocan prevent waste of electrical power

Load-sensing systems such as those referred to, above, have been used tomonitor the electrical power factor of a motor. It has now beendiscovered that when a motor controlled by a load-sensor is connected tooperate a circulation pump such as those used in swimming pools and thelike, the load-sensor can operate in a new way as an SVRS. Despite thefact that the pump remains charged with water during a vacuum entrapmentevent, the motor changes shaft speed in a manner that the load-sensordetects. Shaft speed increases as load is reduced. Thus, the load-sensorbecomes a monitor for motor shaft speed (RPM).

Suitable load-sensors are generally disclosed by U.S. Pat. No. 4,123,792to Gephart et al., issued Oct. 31, 1978, U.S. Pat. No. 4,419,625 toBejot et al., issued Dec. 6, 1983, U.S. Pat. No. 5,473,497 to Beattyissued Dec. 5, 1995, and U.S. Reissue Pat. RE 33,874 to Miller issuedApr. 7, 1992. Each of these patents is incorporated by reference hereinfor disclosure of load-sensor technology.

A load-sensor measures the power factor of a motor. The load-sensoroutput can produce an accurate reading of the percentage of theelectrical current passing through the motor that is converted intouseful load or power that is transferred to the attached circulationpump. Load-sensors are commercially produced as stand alone componentsthat can be attached to any motor. In addition, some motors include anintegrated load-sensor. Particularly the latter allows the substitutionof a motor with integral load-sensor into a space that previously houseda motor without load-sensor.

During an aquatic suction entrapment event, a trapped bather or otherblockage stops water flow into a suction outlet fitting of an aquaticfacility. Typically, in order for suction entrapment to occur, thecirculation pump must have become single-sourced to a single suctionoutlet fitting, such that the pump receives all intake of water from thesingle fitting. When the blockage closes off the final suction outletfitting, vacuum or negative pressure abruptly increases within theintake pipe to the circulation pump. The high level of vacuum iscommunicated from the pump to the victim through the conduit thatconnects the pump to the blocked suction outlet fitting inside of theswimming pool.

Simultaneously with the entrapment event, water flow within thecirculation system abruptly decreases or stops. As a result, the pump ismoving a substantially decreased volume of water. Correspondingly, theelectric pump motor sees an abruptly decreased load accompanied by acorresponding increase in RPM. The load-sensor on the pump motor sensesthe aquatic suction entrapment event by detecting the abruptly decreasedload factor for the electric motor that drives the circulation pump.This method of operating an SVRS eliminates the need to monitor vacuumlevel for the intake line.

The load-sensor is configured to shut off the circulation pump motorupon detecting a predetermined level of motor underload condition.Extensive testing has established that a motor underload condition willresult as a reliable indication of a flow blockage at the pump intakethat is severe enough to be unsafe for bathers. Thus, a load-sensorcontrolling a motor and monitoring underload condition will perform asan SVRS that, in the event a bather has become trapped, shuts off themotor and hence the circulation pump. With the circulation pump stopped,the resulting dangerously high level of vacuum quickly neutralizes. Bythe use of normal controls, the motor and load-sensor can be configuredto require either a manual reset or automatic reset after apredetermined amount of time, such as five minutes, has elapsed sincethe load-sensor shut off the motor.

In one embodiment of the disclosure, a load-sensor is integrated withinthe circulation pump motor at the time of manufacture. Such a motor canbe easily and universally fit into any swimming pool, because allswimming pools have a circulation pump motor.

This SVRS load-sensor is specifically adjusted to shut off the motor inan underload situation. Extensive testing has shown that underload isindicative of a characteristic loss of water flow and motor RPM increasethat accompanies a suction entrapment event. Further, the load-sensormust be adjusted to reliably pass official standards for SVRS devices.Testing standards bodies such as ASTM or ANSI establish a standard forSVRS performance without failure. These standards provide the officialprotocol for testing an SVRS in order to gain ASTM or ANSI approval. Theprocedure calls for testing the SVRS in a variety of hydraulicsituations. Water is supplied to a test pump from a single, standard,eight-inch aquatic suction outlet fitting. With the test pump inoperation, a blocking element with fifteen pounds of buoyancy isrepeatedly placed over the suction outlet fitting to simulate a seriesof suction entrapment events. The SVRS must successfully release theblocking element within 3 seconds to 4.5 seconds (depending on thelength of pipe) in each and all of the tests without failure.

When a suction entrapment event occurs, a bather has blocked the waterflow into a suction outlet fitting within a swimming pool, stopping flowto the circulation pump. The stoppage of water flow causes the pump tocreate an extremely high level of vacuum at the pump intake. This highlevel of vacuum is transmitted through the stationary water within thesuction pipe to the suction outlet fitting, where the victim has becometrapped. Typically, any standard swimming pool pump, regardless of thehorsepower rating of the pump motor, will create in excess oftwenty-four in HgR (inches of mercury relative) (˜11.8 psi) vacuum whenthe pump intake is blocked. Every square inch of area of adhesionbetween the fitting and the victim has an adhesion force of over elevenpounds. This vacuum or negative pressure, rather than the loss of waterflow, is the lethal force that can cause an accident such as injury ordrowning death to a bather.

When a suction entrapment event occurs, the vacuum level increases andthe flow of water decreases within the suction pipe. The vacuum level isinversely proportional to the flow of water. The load or powertransferred by the electric motor to the pump is directly proportionalto the flow of water but not to the vacuum level nor to the relativefluid pressure within the circulation system. The SVRS senses the load,which is fundamentally determined by the volume of water flowing throughthe pump. Therefore, when a bather is trapped, and in contrast to priorart SVRS, this SVRS reacts to the loss of water flow rather than to anincrease in vacuum level. The disclosure includes this new method foroperating an SVRS.

In one embodiment, the SVRS operates to detect a suction entrapmentevent by sensing the percentage of electrical power being consumed bythe pump motor. The load-sensor converts this sensed value to load orpower factor. In an SVRS with programmable operation, a shut off settingtypically in the range from 55% to 62% has been found suitable andappropriate. If suction flow blockage occurs, the water flow to the pumpis interrupted or greatly restricted. The electric pump motor isunderloaded. In this situation, the load-sensor senses the underloadcondition and shuts off the pump motor. As a result, the high vacuumlevel created by the operating pump, accompanying the flow blockage,neutralizes, thereby releasing the victim.

A novel aspect of the disclosure is that the SVRS reacts to hydraulicsituations within the pump without having any direct fluid communicationwith the water flow path.

With reference to FIG. 1, an aquatic facility or vessel such as aswimming pool 10 includes a water circulation system 1. A speciallyconfigured circulation pump 12 operates this system. Normally the pump12 is a centrifugal pump. One or more conduits or suction lines such aspipelines 14 are connected for communication between the pool and theintake side of pump 12, such that the pump 12 draws water throughpipelines 14. Various suction outlet fittings at the pool provide waterinto the pipelines 14.

For example, a skimmer 16 provides water from the typical water surfacelevel 17 when the pool is full. A skimmer includes a basket 18 forcatching floating debris from the pool surface. A weir 20 helps toretain the debris in the skimmer. Below the basket, a float valve 22controls the skimmer, and a section equalizer line 24 connects thebottom of the skimmer back to the pool.

A circulation drain 26 on the bottom of the pool provides water to thepump 12. A second drain 28 is beneficial for safety reasons, to helpavoid suction entrapment that could be caused by a single-source pumpintake. Pool drains 26, 28 should include suction outlet safety covers30.

The circulation system 1 directs water flow through a circuit. Suctionvalve manifolds 32 between the pool and the intake side of the pumpcontrol incoming flow. The outlet side of the pump feeds water to afilter 34. In turn, water flows from the filter to an optional heater36. In some circulation systems 1, a check valve 38 might be installedbetween the heater 36 and filter 34 to prevent reverse flow of heatedwater into the filter. Check valves 38 should be removed to better allowvacuum level to neutralize quickly when the pump motor stops. Afterpassing through the filter and heater, the water flows back into thepool through a return line 40.

Suction entrapment can occur if the pump 12 becomes single-sourced,drawing all of its water from one suction outlet fitting, such as at asingle drain 26. A pump can become single-sourced by a variety ofcircumstances. For example, a skimmer 16 sometimes is installed withoutan equalizer line 24. The omission of the equalizer line 24 allows aplugged basket 18 to block the skimmer 16. Similarly, a low water level42 or a jammed weir 20 can close the float valve 22. In any of thesecircumstances, the skimmer 16 ceases to perform as a water source topump 12 and contributes to the possibility that the pump will becomesingle-sourced.

A variety of other events can result in the pump 12 becomingsingle-sourced or otherwise contribute to a suction entrapment event.Dual drains 26, 28 can provide a measure of safety against the pumpbecoming single-sourced. However, if two bathers simultaneously blockthe dual drains, entrapment can occur. Pool control valves such assuction valve manifolds 32 accidentally can be set for single-sourcedoperation. In circulation systems 1 where check valve 38 has not yetbeen removed, the check valve can interfere with the operation of anSVRS by maintaining the high vacuum even after the pump motor is shutoff. Consequently, check valves 38 should be removed from a circulationsystem 1. Missing suction outlet safety covers 30 also can contribute tothe likelihood of a suction entrapment event.

If a bather should block the single-source fitting, an entrapmentaccident can result. Swimming pool pumps can be quite powerful ascompared to pumps used only a few decades ago, causing an increased riskof suction entrapment. A standard eight-inch drain cover, ifsingle-sourced to a one horsepower pump, can produce three hundred fiftypounds of entrapment force. A twelve-inch drain cover can transmit oversixteen hundred pounds of adhesion force to an entrapped victim.

An electric motor 44 powers the circulation pump 12. Motor 44 typicallyis connected to a power source 46, such as an AC power grid, forexample, to draw line voltage and current. A load-sensor 48 operates todetect underload and to shut off the motor when underload is detected.The load-sensor 48 controls a switch 50 that shuts off the motor fromthe AC grid. Motors with built-in load-sensors are produced by variouscommercial sources.

As an example of a modern, commercial load-sensor, the block diagram ofFIG. 2 shows a motor system 44 of impedance 52 in combination with aload-sensor system 48 suitable to shut off the electric motor systemupon detecting a suitable underload. The load-sensor 48 detects motorunderload when coupled to reference levels. The load-sensor 48 developsfirst and second electrical signals indicative of first and secondparameters of power delivered to the load, pulse width modulates thefirst electrical signal to produce a pulse width modulated firstelectrical signal, and modulates the second electrical signal inaccordance with the pulse width modulated first electrical signal toproduce a power waveform. The load-sensor 48 then integrates the powerwaveform to produce an output signal indicative of the energy deliveredby the motor 44 to the load.

Pulse width modulator 54 senses the line voltage appearing across theimpedance 52 and produces a voltage signal that is a pulse widthmodulated version of the line voltage. This pulse width modulatedvoltage signal is developed at a pulse width modulator output 56. The ACline voltage is modulated by the pulse width modulator 54 during each ofeither the positive half-cycles or negative half-cycles of the linevoltage so that the pulse width modulated voltage signal comprises a setof pulses at times corresponding to each of either the positivehalf-cycles or negative half-cycles and a value of zero at timescorresponding to the other of the positive half-cycles or negativehalf-cycles.

A current sensor 58 detects the line current that flows through themotor 44 and delivers a current signal indicative of line current to aswitch 60. The switch 60 modulates the current signal and is controlledin accordance with the pulse width modulated voltage signal produced bythe pulse width modulator 54 at the pulse width modulator output 56 suchthat the switch 60 is closed during each pulse of the pulse widthmodulated voltage signal and is open at all other times. In this manner,the switch 60 effectively multiplies the voltage appearing across themotor impedance 52 with the current flowing through the motor 44 duringevery other half-cycle of the line voltage to produce a modulatedcurrent signal indicative of the real power delivered by the powersource 46 to the motor 44.

An integrator 62 integrates the modulated current signal developed bythe switch 60 to produce an energy waveform that is indicative of theenergy delivered to the motor 44 during each positive half-cycle ornegative half-cycle of the line voltage and, therefore, that isindicative of the energy delivered by the motor 44 to pump 12. Theenergy waveform developed by the integrator 62 is delivered to a switchcontroller 64 that latches the final value of the energy waveform inresponse to a signal developed, for example, on a line 66, and comparesthe latched value with a predetermined level to detect a motor underloadcondition. If the amplitude of the energy waveform is below apredetermined reference level, an underload condition is detected andthe switch controller 64 opens the switch 50 to disconnect the powersource 46 from the motor 44. In this manner, the motor 44 provides thefunction of an SVRS during a suitable underload condition.

The integrator 62 is reset by a microprocessor 70 in conjunction with aswitch 72. The microprocessor 70, which inherently contains or enables aclock function or timing means, counts the cycles of the line voltageappearing across the impedance and produces a reset signal after apredetermined number of line cycles. The reset signal closes the switch72 in order to reset the integrator 62 and thereby to reset the energywaveform to a value of zero. The microprocessor 70 can reset theintegrator 62 every half-cycle so that the integrator 62 produces anenergy waveform indicative of the energy delivered to the motor 44during any particular line voltage half-cycle or, alternatively, themicroprocessor 70 can reset the integrator 62 after a predeterminednumber of line cycles. The latter configuration enables the integrator62 to integrate the modulated current signal produced by the switch 60over a number of consecutive line cycles, enabling the load-sensor 48 tomeasure comparatively small amounts of energy over a number of linecycles to produce an accurate indication of the motor loading condition.The microprocessor 70 produces a latching signal on the line 66 prior toresetting the switch 72. The latching signal enables the switchcontroller 64 to latch the energy waveform produced by the integrator62.

Alternatively, the operation of the switch controller 64 can beperformed by the microprocessor 70. In this alternative, the output ofthe integrator 62 is converted into a digital signal by an ND converter(not shown). The digital signal is provided to the microprocessor 70,which determines whether an underload condition exists by comparing thesignal with a reference load value. In this alternative, themicroprocessor 70 directly controls the switch 50 in order to disconnectpower from the motor 44 when an underload condition occurs.

In load-sensors using a microprocessor 70, programming readily sets theshut off period of the switch controller 64. For use as an SVRS, theprogramming should call for a predetermined shut off period on the orderof five minutes. This period provides adequate time to an entrappedbather to recover and remove himself from the suction outlet fitting.Thus, it is adequate and acceptable for the circulation pump motor torestart automatically after a five-minute shut off cycle. Themicroprocessor 70 can monitor the shut off period by use of itscontained timing function. After the predetermined period, themicroprocessor can signal the switch controller 64 to close switch 50and thereby restart the pump motor 12.

The present disclosure also relates to an SVRS for an aquatic facilitywhich incorporates an electronic flow-rate indicator operativelyconnected to a circulation system of an aquatic facility. A flow-rateactivated SVRS functions substantially similar to the load-sensing SVRSdescribed above. The flow-rate activated SVRS, however, relies upon themeasured flow-rate of the water within the circulation system 1 toidentify and remedy a suction entrapment event. By way of example andnot limitation, a flow-rate activated SVRS continuously measures therate of flow of water within the circulation system 1. If the flow-rateactivated SVRS measures a flow-rate that falls outside of a normaloperating range, thereby indicating an abnormal blockage at an intake,the system interrupts the power supplied to the circulation pump inorder to stop the pump to break the vacuum at the intake.

FIG. 3 is a schematic diagram of a flow-rate activated SVRS 100according to one embodiment. The flow-rate activated SVRS 100 includes acontrol device 102 that is in communication with a flow-rate sensor 104,a pool circulation pump 12, a computing device 200, and a power source46. In addition, the control device could include optionally a pump andheater time clock to set daily swimming pool filtration cycles. In oneembodiment, the computing device 200 is incorporated into the controldevice 102. In one embodiment, the system shown in FIG. 3 may beincorporated into the aquatic system of FIG. 1. For example, theflow-rate sensor 104 may be incorporated between the pool circulationpump 12 and the filter 34 of FIG. 1. Thus, in this embodiment, theflow-rate activated SVRS works in conjunction with the load-sensor SVRSdescribed above. In alternate embodiments, the flow-rate SVRS mayprovide the safety measures described without the load-sensor.

In various embodiments, the control device 102 may also include adisplay device 106 and an input device 108 and may be located remotelyfrom the circulation system 1. The display device 106 may be an LCDdisplay that is incorporated in to the control device 102. In otherembodiments, the display device 106 may be external to the controldevice 102 and may be any display device suitable for displaying data.The input device 108 may be as a keyboard or a pointing device (e.g., amouse, trackball, pen, or touch pad), for receiving input at the controldevice 102. One or both of the display device 106 and the input device108 may be incorporated in to the control device 102. Alternately, oneor both of the display device 106 and the input device 108 may externalto but in communication with the control device 102.

The flow-rate sensor 104 measures the flow-rate of water travelingthrough the circulation system 1 of the aquatic facility. The flow-ratesensor 104 may also measure the velocity of water traveling through thecirculation system 1. The flow-rate sensor 104 can be attached to thecirculation system 1 of the aquatic facility such that the sensor isnon-invasive to the circulation system 1. For example, the flow-ratesensor 104 may be clamped onto a pipe of the circulation system. Invarious embodiments, the flow-rate sensor 104 may be connected to adischarge pipe 110 of the circulation pump. In general, however, theflow-rate sensor 104 may be incorporated anywhere along the circulationsystem 1 to measure the rate of flow of water through the system.

A number of commercially available off the shelf electronic flow-ratesensors may be employed in accordance with the teachings as herein setforth including, a Doppler Ultrasonic Flow Meter and a Transit TimeUltrasonic Flow Meter, both manufactured by Dynasonics of RacineFederated Inc., of Racine, Wis. and Shenitech LLC of Woburn, Mass. Byway of illustration and not by limitation, other types of flow-ratesensors including, magnetic paddlewheel, vortex shedding, turbine,deflector, ultrasonic transit time, ultrasonic Doppler, and differentialpressure sensors may be used. In a preferred embodiment, an ultrasonictransit time flow-sensor would be employed, inasmuch as ultrasonicflow-sensors are accurate, dependable, and non-invasive (e.g. installedby clamping onto the discharge pipe 110 without coming into contact withthe water).

In one example, a Doppler-ultrasonic flow meter or a transit timeultrasonic flow meter is attached to the outside surface of the pumpdischarge pipe 110 of the circulation pump 12 of the aquatic facility tomeasure the flow-rate through the pipe non-invasively. This arrangementallows the flow-rate to be determined without direct interference in thecirculation system 1. Moreover, the flow-rate sensor 104 may be attachedeasily and at little cost, by using an injection-molded plastic clipthat snaps onto the discharge pipe 110. In addition, because theflow-rate sensor 104 provides the actual water flow-rate through thecirculation system 1, the cutoff threshold can be set at a level thatreduces the occurrences of false tripping of the switch 50 thatdisconnects power supplied to the pump motor 44. In one example, thecutoff threshold may be set at 20-30 gallons per minute (GPM), whichwould provide the pump 12 a greater operating range, thereby reducingthe occurrence of inadvertent tripping of the switch 50 due to thechanges in the rate of flow under normal swimming pool operation.

The flow-rate sensor 104 is robust in relation to the types and numberof pumps and circulation systems from which the flow-rate can bemeasured, as the flow-rate sensor is independent of vacuum and pressurelevels within the circulation system 1. Any suitable flow-rate sensors,such as the flow-rate sensor 104, may be used regardless of the pumplocation relative to the water level of the aquatic vessel.

The flow-rate activated SVRS 100 may further incorporate a delaymechanism (not shown) that allows the pump 12 to be restarted after ahigh vacuum level has been detected and the pump has been shut off. Inone embodiment, a timer (not shown) may disable the pump shut-offresponse for a specified amount of time when the pump is first poweredup. For example, the delay may disable the shut off mechanism while thepump primes and accelerates water to a stable flow-rate. In oneembodiment, the delay mechanism and/or timer may be incorporated intothe control device 102. The system 100 may also verify that the flowthrough the circulation system 1 has exceeded the cut-off level and theninitiates the safety vacuum release feature to reduce the vacuumpressure level in the event a slow blockage occurs. Additionally, anautomatic restart feature may be incorporated into the system thatattempts to restart the system a specified amount of time after thesafety vacuum release feature has been activated. This automatic restartfeature may prevent the water from stagnating in a situation where thepump has been shut off by the SVRS.

In operation, the computing device 200 may execute one or more softwareprograms and/or applications which determine and monitor the maximum andminimum flow-rates allowed by the circulation system 1. In addition, thecomputing device may read a computer-readable medium encoded withinstructions, one or more software programs, or applications todetermine and monitor the maximum and minimum flow-rates allowed by thecirculation system 1. Data regarding the maximum and minimum flow-ratelimits may be stored within memory 216 of the computing device 200. Ifthe real-time flow-rate exceeds either of these limits, the controldevice 102 interrupts the power from the power source 46 by generating asignal or opening a relay to the pump motor 44 to stop the operation ofthe pump 12. In one embodiment, the computing device 200 ispreprogrammed, such that the only on-site programming required would beto indicate the nominal pipe diameters for the circulation system 1. Byway of example and not limitation, the circulation system may use pipeshaving nominal diameters of 1.25″, 1.5″, 2.0″, 2.5″, 3.0″, or 4.0″.

In one embodiment, the control device 102 receives the signals from theflow-rate sensor and displays the water flow-rate, in real-time, on thedisplay device 106; although other means of displaying flow-rate may beused without departing from the scope of the present disclosure. Inanother embodiment, the computing device 200, as shown in FIG. 4,receives and processes data from the flow-rate sensor 104. The computingdevice 200 also transmits data from the flow-rate sensor 104 inreal-time to the display device 106.

Alternately, the control device 102 could be programmed to provide thepool operator with a real-time turnover rate. In general, the turnoverrate is the amount of time, typically expressed in hours, for the totalvolume of the swimming pool 10 to pass through the filter 34. Thecomputing device 200 may be programmed with data related to pool volume,and then the control device 102 may display the real-time turnover ratein hours. The computing device 200 may also be programmed to provide thereal-time percentage of clean filter flow. Therefore, the control device102 may then display what percentage of the current flow-rate is equalto the clean flow-rate.

Other features may also be programmed or otherwise included in theflow-rate activated SVRS 100. For example, as described above, thecontrol device 102 may be configured to provide an indication of a dirtyfilter in the circulation system 1 of the aquatic vessel. In oneembodiment, the dirty filter indicator may be provided when theflow-rate of the circulation system 1 has dropped to 50% of clean filterflow-rate. In another example, the control device 102 may be programmedto control the pump 12 to maintain an optimum flow-rate through thecirculation system 1 by gradually increasing the pump speed as hydraulicresistance to the flow is increased due to a dirty filter. In yetanother example, the control system may include a freeze preventerfeature that would activate the pump to circulate water through thesystem in the event that the ambient air temperature drops below aspecified temperature. For example, in one embodiment, the controlsystem may activate the pump when the ambient air temperature dropsbelow 40 degrees F. to prevent freeze damage to the circulation system1.

The methods and operations of the flow-rate activated SVRS 100 describedherein may be performed by the control device 102 that includes or is atleast in communication with the computing device 200. FIG. 4 is a blockdiagram of the computing device 200 for operating the flow-rateactivated SVRS 100 according to one embodiment. The computer system(system) includes one or more processors 202-206. Processors 202-206 mayinclude one or more internal levels of cache (not shown) and a buscontroller or bus interface unit to direct interaction with theprocessor bus 212. Processor bus 212, also known as the host bus or thefront side bus, may be used to couple the processors 202-206 with thesystem interface 214. System interface 214 may be connected to theprocessor bus 212 to interface other components of the computing device200 with the processor bus 212. For example, system interface 214 mayinclude a memory controller 218 for interfacing a main memory 216 withthe processor bus 212. The main memory 216 typically includes one ormore memory cards and a control circuit (not shown). System interface214 may also include an input/output (I/O) interface 220 to interfaceone or more I/O bridges or I/O devices with the processor bus 212. Oneor more I/O controllers and/or I/O devices may be connected with the I/Obus 226, such as I/O controller 228 and I/O device 230, as illustrated.

I/O device 230 may also include an input device (not shown), such as analphanumeric input device, including alphanumeric and other keys forcommunicating information and/or command selections to the processors202-206. Another type of user input device includes cursor control, suchas a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to the processors 202-206and for controlling cursor movement on the display device.

The computing device 200 may include a dynamic storage device, referredto as main memory 216, or a random access memory (RAM) or othercomputer-readable devices coupled to the processor bus 212 for storinginformation and instructions to be executed by the processors 202-206.Main memory 216 also may be used for storing temporary variables orother intermediate information during execution of instructions by theprocessors 202-206. The computing device 200 may include a read onlymemory (ROM) and/or other static storage device coupled to the processorbus 212 for storing static information and instructions for theprocessors 202-206. The system set forth in FIG. 2 is but one possibleexample of a computer system that may employ or be configured inaccordance with aspects of the present disclosure.

According to one embodiment, the above techniques may be performed bycomputing device 200 in response to processor 204 executing one or moresequences of one or more instructions contained in main memory 216.These instructions may be read into main memory 216 from anothermachine-readable medium, such as a storage device. Execution of thesequences of instructions contained in main memory 216 may causeprocessors 202-206 to perform the process steps described herein. Inalternative embodiments, circuitry may be used in place of or incombination with the software instructions. Thus, embodiments of thepresent disclosure may include both hardware and software components.

A machine readable medium includes any mechanism for storing ortransmitting information in a form (e.g., software, processingapplication) readable by a machine (e.g., a computer). Such media maytake the form of, but is not limited to, non-volatile media and volatilemedia. Non-volatile media includes optical or magnetic disks. Volatilemedia includes dynamic memory, such as main memory 216. Common forms ofmachine-readable medium may include, but is not limited to, magneticstorage medium (e.g., floppy diskette); optical storage medium (e.g.,CD-ROM); magneto-optical storage medium; read only memory (ROM); randomaccess memory (RAM); erasable programmable memory (e.g., EPROM andEEPROM); flash memory; or other types of medium suitable for storingelectronic instructions.

For the various embodiments, a number of experiments were conducted todetermine the operating range for the SVRS and to verify the consistencyof operation under a variety of conditions. In one such experiment, aShenitech™ ST301 Transit Time Flow Meter was used as the flow-ratesensor in an embodiment of the flow-rate activated SVRS. The SVRS wasprogrammed to shut off the circulation pump 12 when the water flow inthe circulation system 1 dropped below 20 GPM.

Various combinations of pump horsepower, pump elevation (relative to thewater level of the pool), and line voltages were tested under conditionswhere the flow of water gradually decreased or was abruptly restrictedwithin in-line valves of the pump suction intakes and the pump dischargepipes. These various combinations and conditions were chosen to simulatereal life blockages in an aquatic facility. The actual pump shut offpoints (in GPM) are presented below in table 1.

TABLE 1 PUMP ELEVATION TO RESERVOIR WATER LEVEL Center of Pump Intake toReservoir WL 24″ Above WL At WL 18″ Below WL 1 HP Pump at 208 V LineVoltage PUMP SUCTION INTAKE BLOCKAGE 20 GPM 20 GPM 20 GPM PUMP DISCHARGEBLOCKAGE 20 GPM 20 GPM 20 GPM 1 HP Pump at 240 V Line Voltage PUMPSUCTION INTAKE BLOCKAGE 20 GPM 20 GPM 20 GPM PUMP DISCHARGE BLOCKAGE 20GPM 20 GPM 20 GPM 2 HP Pump at 208 V Line Voltage PUMP SUCTION INTAKEBLOCKAGE 20 GPM 20 GPM 20 GPM PUMP DISCHARGE BLOCKAGE 20 GPM 20 GPM 20GPM 2 HP Pump at 208 V Line Voltage PUMP SUCTION INTAKE BLOCKAGE 20 GPM20 GPM 20 GPM PUMP DISCHARGE BLOCKAGE 20 GPM 20 GPM 20 GPM

During the experiments, a programmable flow-rate damper was set at zero(0) seconds to achieve a fast pump shut-off. As shown, the flow-rateactivated SVRS of the present disclosure accurately shut off thecirculation pump when the flow-rate sensor measured a flow-rate below 20GPM in all experimental combinations.

In addition, during the gradual pump discharge blockage experiments, thecirculation pump produced vapor bubbles which caused the flow-ratesensor to read values approximately 30% above the actual flow-rates atflow-rates below 35 GPM. Therefore, based on these experiments variousembodiments of the flow-rate activated SVRS may be programmed accordingto the power of the circulation pump as provided in Table 2.

TABLE 2 PUMP LOW FLOW HORSEPOWER SHUT OFF .75 HP/1-Speed 20 GPM 1.0HP/1-Speed 22 GPM 1.5 HP/1-Speed 25 GPM 2.0 HP/1-Speed 28 GPM 3.0HP/1-Speed 30 GPM 3.0 HP/Variable 30 GPM

The foregoing is considered as illustrative only of the principles ofthe disclosure. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe disclosure to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be regarded as falling within the scope of the disclosure.

1. An aquatic facility with a safety vacuum release system, comprising:an aquatic vessel configured to contain a body of water suitable forbathing; a circulation system for circulating the water, wherein thecirculation system includes: at least one circulation intake; acirculation pump having a pump intake in fluid communication with thecirculation intake and a pump output in fluid communication with acirculation output for directing the water back into the aquatic vessel;and an electric motor for operating the circulation pump; a flow-ratesensor in communication with the circulation system to measure the rateof flow of the water circulated by the circulation system; and thesafety vacuum release system in communication with the circulationsystem and the flow-rate sensor, the safety vacuum release system tointerrupt the operation of the circulation pump by interrupting anelectrical power source in response to a particular flow-rate measuredby the flow-rate sensor.
 2. The aquatic facility of claim 1, wherein theflow-rate sensor is selected from a group consisting of a magneticpaddlewheel sensor, a vortex shedding sensor, a turbine, a deflector, anultrasonic transit time sensor, and an ultrasonic Doppler sensor, and adifferential pressure sensor.
 3. The aquatic facility of claim 1 furthercomprising a control device having a processor, memory, a displaydevice, and an input device, the memory storing a minimum allowableflow-rate value and a maximum allowable flow-rate value.
 4. The aquaticfacility of claim 3 wherein the control device receives data signalsfrom the flow-rate sensor and displays the flow-rate of the water inreal-time on the display device.
 5. The aquatic facility of claim 4wherein the processor receives and processes data regarding the rate offlow of the water and transmits processed data to the display device inreal-time.
 6. The aquatic facility of claim 3 wherein one or moresoftware programs executes on the processor, the software program togenerate a signal to terminate the operation of the circulation pump,when the received rate of flow of water falls outside of a range definedby the minimum allowable flow-rate value and the maximum allowableflow-rate value.
 7. The aquatic facility of claim 3 wherein the controldevice displays a turnover rate for the body of water.
 8. The aquaticfacility of claim 3 wherein the control device displays a percentage ofthe flow-rate that corresponds to a flow-rate corresponding to a cleanfilter.
 9. The aquatic facility of claim 3 wherein the control devicedisplays a percentage of the flow-rate that corresponds to a flow-ratecorresponding to a dirty filter.
 10. A flow-rate activated safety vacuumrelease system comprising: a circulation system for an aquatic vessel; aflow-rate sensor operably engaged to the circulation system andconfigured to determine a rate of flow through the circulation system;and a control system in communication with the flow-rate sensorconfigured to receive a signal related to the flow-rate through thecirculation system and provide one or more control signals to control apump of the circulation system.
 11. The flow-rate activated safetyvacuum release system of claim 10 wherein the one or more controlsignals enable or disable power to be received at the pump.
 12. Theflow-rate activated safety vacuum release system of claim 10 wherein theone or more control signals for the pump are generated in response to ahydraulic resistance causing a loss of flow of water within thecirculation system caused by a dirty filter.
 13. The flow-rate activatedsafety vacuum release system of claim 12 wherein the one or more controlsignals maintain a substantially constant rate of flow of water withinthe circulation system.
 14. A method for automatically releasing abather trapped submerged within an aquatic vessel having a watercirculation system, the trapped bather being held by a suction at asubmerged suction outlet fitting of the water circulation system, themethod comprising: circulating water in the water circulation systemwith a pump powered by an electric motor, the water circulation systemhaving a normal operating range defined by a minimum allowable flow-rateand a maximum allowable flow-rate; identifying an occurrence of anexcessive vacuum pressure within the submerged intake of the watercirculation system; and decreasing the excessive vacuum pressure withinthe submerged intake by interrupting the power applied to the pump,whereby decreasing the excessive vacuum pressure within the submergedsuction outlet fitting releases the trapped bather from the suction atthe submerged suction outlet fitting.
 15. The method of claim 14,wherein identifying an occurrence of an excessive vacuum pressure occursautomatically and remotely from the submerged suction outlet fitting ata control device having at least one processor.
 16. The method of claim14, wherein decreasing the excessive vacuum pressure within thesubmerged intake occurs without introducing air to the water circulationsystem.
 17. The method of claim 14, further comprising: displaying anactual water flow-rate of water in the water circulation system at acontrol device.
 18. The method of claim 18 wherein the actual real-timeflow-rate of the water within the water circulation system is displayedin real-time.
 19. A computer-readable medium encoded with instructionsexecutable by a processor for a method to automatically release a bathersuction entrapped within an aquatic vessel having a water circulationsystem, the trapped bather being held by a suction at a submergedsuction outlet fitting of the water circulation system, the methodcomprising: circulating water in the water circulation system with apump powered by an electric motor, the water circulation system having anormal operating range defined by a minimum allowable flow-rate and amaximum allowable flow-rate; identifying an occurrence of an excessivevacuum pressure within the submerged suction outlet fitting of the watercirculation system; and decreasing the excessive vacuum pressure withinthe submerged intake by interrupting the power applied to the pump,whereby decreasing the excessive vacuum pressure within the submergedintake releases the trapped bather from the suction at the submergedsuction outlet fitting.
 20. The method of claim 19, wherein identifyingan occurrence of an excessive vacuum pressure occurs automatically andremotely from the submerged intake at a control device having theprocessor.
 21. The method of claim 19, further comprising: displaying anactual water flow-rate of water within the water circulation system at acontrol device.
 22. The method of claim 21 wherein the actual flow-rateof water within the water circulation system is displayed in real-time.